The overall aim of this study is to determine if the calcium intake recommended during pregnancy is sufficient to provide for the high calcium requirements of two groups of high-risk pregnancies, adolescent singleton gestation and adult multiple gestations. The study will determine whether specific abnormalities of calcium and of the calcium regulating hormone, parathyroid hormone (PTH) and 1,25 (OH)2 Vitamin D, the active metabolite of vitamin D (calcitriol), are related to calcium intake in adolescent pregnancies and adult multiple gestation. This study may provide important information that could lead to the understanding of the possible increased calcium needs of these two highly important groups of pregnancies, and provide important information that could lead to the reduction of high blood pressure during pregnancy. This project utilizes the resources of the CRC Core Laboratory only for the above-mentioned determinations. There are no inpatient or outpatient visits.